1. Field of the Invention
The present invention relates to a liquid crystal display and, more particularly, to a vertically aligned mode liquid crystal display where a pixel region is partitioned into a plurality of micro-domains to obtain a wide viewing angle.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) has a structure where a liquid crystal bearing dielectric anisotropy is sandwiched between a color filter substrate and a thin film transistor (TFT) array substrate. The color filter substrate has a common electrode, color filters and a black matrix, and the TFT array substrate has a TFT and a pixel electrode. An electric field is applied to the liquid crystal while being varied in strength, thereby controlling the light transmission and displaying the desired picture image.
Such a LCD usually involves a narrow viewing angle. In order to obtain a wide viewing angle, various techniques have been developed. Among such techniques, it has been proposed that the liquid crystal molecules are vertically aligned with respect to the substrates while forming opening or protrusion patterns at the pixel electrode and the common electrode facing each other.
In the opening pattern formation technique, an opening pattern is formed at the pixel electrode and the common electrode, respectively. Fringe fields are formed due to the opening patterns, and the inclining direction of the liquid crystal molecules is controlled by way of the fringe fields, thereby widening the viewing angle.
In the protrusion formation technique, a protrusion is formed at the pixel electrode and the common electrode, respectively. The electric field formed between the pixel electrode and the common electrode is deformed due to the protrusions, thereby controlling the inclining direction of the liquid crystal molecules.
Furthermore, it is also possible that an opening pattern is formed at the pixel electrode, while a protrusion is formed at the common electrode. Fringe fields are formed due to the opening pattern and the protrusion, and the inclining direction of the liquid crystal molecules is controlled by way of the fringe fields, thereby partitioning the pixel region into a plurality of micro-domains.
In such a multi-domain LCD, the contrast ratio-based viewing angle, or the gray scale inversion-based viewing angle is 80° or more in all directions, which is an excellent result. The contrast ratio-based viewing angle takes a contrast ratio of 1:10 as a reference value, and the gray scale inversion-based viewing angle is defined as a limitation angle of inter-gray scale brightness inversion. However, the LCD bears side gamma curve deformation where the center gamma curve and the side gamma curve are not agreed upon, and hence, involves deteriorated visibility from the left and right sides even when compared to a twisted nematic (TN) LCD.
For instance, in the case of a patterned vertically aligned (PVA) mode where an opening pattern is formed to obtain multiple domains, as the viewing angle becomes larger, the screen becomes brighter and the color becomes whiter. In an extreme case, the difference in distance between the bright gray scales is dissipated so that the picture image seems to be collapsed.
As the LCD has been recently developed for use in a multi-media use, it is desirable that still or motion picture images should be displayed with enhanced visibility.